Electromagnetic structure with low reluctance u-shaped pole means



Sept. 26, 1967 c. T. ROBINS ETAL 3,344,375

ELECTROMAGNETIC STRUCTURE WITH LOW RELUCTANCE U-SHAPED POLE MEANS Flled Sept 13, 1965 INVENTORS (#42465 [Pose/Ms BY h fsra/v M aoa kon United States Patent 3 344 375 ELECTROMAGNETIC STRUCTURE WITH Low 1 RELUCTANCE U-SHAPED POLE MEANS Charles T. Robins, Swarthmore, Pa., and Weston W.

Goodnow, Moorestown, N.J., assignors to I.T.E. Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Filed Sept. 13, 1965, Ser. No. 486,815 4 Claims. (Cl. 335--174) ABSTRACT OF THE DISCLOSURE An electromagnetic structure is described, in which the U-shaped pole is formed of complementary L-shaped members, which, upon energization of the magnet, are drawn into intimate contact engagement to minimize the magnetic reluctance of their joint.

Our invention relates to electromagnetic structures in general and more particularly, to a U-shaped magnet and energizing coil which may be assembled in an extremely simplified, rapid and inexpensive manner.

Electromagnetic structures as presently available include a multiplicity of cooperating magnet and armature configurations. One well-known type of structure is of the U-shaped variety, so designated because the magnetic structure includes space separated pole pieces joined by a body section in the general configuration of the letter U. The freely extending ends of the pole face are in turn gap separated from a cooperating armature means which is flux coupled thereto, upon energization of the magnet member. The energizing coil for the magnet is typically in the form of a bobbin having a longitudinally extending central opening. Such U-shaped magnet structures have generally been assembled by winding the bobbin coil directly about the body portion of the U or by staking the pole arms to the U. This manufacturing technique requires special winding machinery or a multiplicity of parts, thereby serving to increase the overall fabrication costs. Further once a particular coil has been wound about its U- shape magnet member, it is quite inconvenient to remove the coil and replace it with one of another rating. Hence, where it is required that a manufacturer stock a complete line of such devices, the various permutations of coil ratings with each of the magnet structures requires a considerable inventory.

Our invention avoids these problems by permiting the bobbin coil winding to be completely Wound independent of its insertion about the body portion of the U-shape magnet structure. After the coil is so wound, the novel U- shape magnet structure of the instant invention is then formed thereabout, with the entire unit being assembled without the utilization of screws, stakes, rivets or other fastening means which serve to complicate and increase the assembly technique. More specifically, the magnetic structure of the instant invention is comprised of two L- shaped magnetic members which include first and second sections joined by a right angle bend. The first sections are inserted in the opposed ends of the bobbin coil assembly, such that they overlap each other in juxtaposed, adjacent planar relation to form the body portion of the U. The respective second sections, which lie in juxtaposition with respect to their respective bobbin ends, will outwardly extend from the body portion, with their free ends lying within a common plane parallel to the body of the U and defining the pole faces. The overlapping sections of the respective magnet members which form the body portion of the U preferably provide a joint of large area and hence of low magnetic reluctance. The body portions are freely positioned within the bobbin coil, such that when the bobbin coil is energized, the magnetic flux passing through the joint pull the respective members together in intimate contact engagement, thus automatically eliminating any small spacing therebetween that might tend to increase the reluctance of the joint. Further, insulative side support members may be interposed between the ends of the bobbin assembly and the magnet pole pieces, with such insulative support members including locating protrusions for maintaining the overall assembly within pocket recesses of the overall unit housing.

The electromagnetic structure of our invention particularly lends itself to compact size arrangements of the type which are required for the actuation of circuit breaker auxiliary trip mechanisms of the general type shown in U.S. patent appliaction, Ser. No. 487,016, in the name of Carl E. Gryctko entitled Circuit Breaker Stack Including Auxiliary Features, filed on even date therewith. Such an electromagnetic structure may be simply assembled of suitable dimensions to be conveniently received within a confined area ofa circuit breaker housing.

It is therefore seen that a principal object of our invention resides in providing an electromagnetic structure of improved simplicity and method of assembly.

A further object of our invention is to provide a U- shaped magnetic structure wherein the energizing coil, located about the body portion of the U may be wound prior to final assembly.

A further object of our invention is to provide a U- shaped magnet structure formed of a pair of L-shaped members, with the legs of the L being formed about the coil in juxtaposed, adjacent planar relationship to define a U configuration.

Still an additional object of our invention is to provide such a U-shape magnet structure which does not require the utilization of screws, stakes, rivets or similar fastening means for the assembly thereof.

These as well as other objects of our invention will become readily apparent upon a consideration of the following description and drawings in which:

FIG. 1 is a cross sectional view of a circuit breaker auxiliary trip device, utilizing an electromagnetic structure in accordance with our invention.

FIG. 2 is a plan view of the electromagnetic structure, along line 22 of FIG. 1 looking in the direction of the arrows.

FIG. 3 is a cross sectional view along line 3-3 of FIG. 2 and looking in the direction of the arrows.

FIG. 4 is an exploded perspective view of the electromagnetic structure constructed in accordance with our invention.

Now referring to the figures, and FIG. I particularly, assembly 10 is a circuit breaker shunt trip device of the type which is the subject of aforementioned US. patent appliaction, Ser. No. 487,016, and utilizes an electromagnetic structure 50, constructed in accordance with the instant invention. It should, however, be understood that this particular application of our invention is for illustrative purposes only, and the broad concepts thereof may be practiced in conjunction with numerous other electromagnetic structures and associated mechanisms.

Shunt trip unit 10 comprises a base 18 of molded insulative material having an open side, capped by a removable cover (not shown) which is also constructed of molded insulating material. The cover is secured to base 18 by a number of spaced rivets 21. Molded base member 18 and cover includes a plurality of pockets which are suitably located for receiving and maintaining the various operating components thereof which will henceforth be described.

A stationary contact member 22 is mounted to con-- ductor member 23 which is, in turn, connected at 24 to input conductor 88. Cooperating with stationary contact 22 is a movable contact 26 which is mounted to the lower end of movable contact arm 27. The upper end of the contact arm abuts a suitable pivot forming formation of manual operating member 28. Manual operating member 28 is pivoted about protrusions 29 thereof which are entered into suitable recesses (not shown) of the molded base 18 and cooperating cover member.

Operating mechanism 30 for bringing about the engagement and disengagement of cooperating contacts 22, 26 comprises latchable cradle 31 which is pivoted at one end thereof at base protrusion 32. One end of cooperating spring 33 is tied to cradle 31 at a point intermediate the ends thereof while the other end of spring 33 is tied to contact arm 27. Operating spring 33 is tensioned, thereby urging contact arm 27 upward into engagement with its pivot or manual operating member 28. The other end of cradle 31 comprises latch tip 34 which is engageable by latch 35 secured to elongated member 36. Elongated member 36 also contains armature member 38 secured thereto by rivet 35', which armature member includes a bifurcated end 39 for movement towards cooperative engagement with the pole faces 76, 86 of our novel electromagnetic structure 50. Conducting braid 40 extends from contact arm 27 to a terminal portion 42 of the electromagnetic structure 50, and is connected to coil end 64 thereof. The opposite coil end 62 is directly connected to external terminal member 58. Elongated member 36 is biased in a clockwise direction by pivot spring 40 disposed in recess 40 of base 18 with one end of spring 40 abutting wall 42 of recess 40 on the other end of spring 40 abutting the portion of elongated member 36 positioned above pivot 37. The normal position of elongated member 36 is set by adjusting screw 43 which extends through an opening in base 18. Screw 43 abuts tensioning member 46, and as it is turned forces tensioning member 46 against elongated member 36 so as to move that member about its pivot 37 for adjusting the armature gap separation.

The tripping of shunt trip device is achieved by energization of electromagnetic actuating coil 52. When coil 52 is energized, the flux path flowing through the magnet members thereof, and particularly, the flux linkage between pole faces 76, 86 and bifurcated end 39 of the armature member 38, urges the armature member 39 into the pole faces. This will effect counterclockwise movement of elongated member 36 about its pivot 37 of a sufiicient magnitude to free the lat-ch member 35 from cradle latch tip 34.

As is fully discussed in aforementioned copending U.S. patent application, Ser. No. 487,016, the unlatching of latchable cradle member 31 is transmitted to a plurality of adjacently stacked devices, closely corresponding to the construction of unit 10. This is achieved by an interconnecting elongated control member 94 which is located within recess 96 of a trip member 92 pivoted at 37. A roller 59 is also pivoted at 60 to cradle 31 such that as the tip 34 of cradle 31 is unlatched from latch 35, cradle 31 moves in a direction striking roller 59 against trip member 92 so as to rotate the latter member counterclockwise about its pivot 37.

Reference is now made to FIGS. 2 through 4 which show in further detail the construction of the electromagnetic structure 50 which encompasses the subject matter of the instant invention. A pair of symmetrical pole members 68, 78 are provided. Magnet pole member 68 includes a first section 70 joined by a right angle bend 74 to its transversely extending second section 72, with there being a pole face 76 at the free end thereof. Similarly, complementary magnet member 78 includes a first section 80 joined by right angle bend 84 to its second section 82 having a second pole face 86 at its free end. A pair of side support members 54, 56 are provided. Side support member 54 includes protrusions 101, 103 which are of a suitable size and spacing to enter cooperating recesses of the molded housing cover. Similarly opposite protrusions 105, 107 of side piece 56 enter recesses of the molded base 18 for positioning assembly 5t). L-shaped members 68, 78 are nested together, such that their leg portions 70 and 80 are freely positioned (or fioat) within opening 63 and are in juxtaposed, adjacent planar relationship. The arm sections 72, 82 outwardly extending therefrom in spaced planar relationship to define a generally U-shape configuration, with the body portions 70, 80 being electromagnetically drawn together in intimate contact engagement, as best shown in FIG. 2. As such, section 70 of the L-shaped member 68 enters the rear region of opening 57 contained within side piece 56 and extends through the rear region of longitudinal central opening 63 of the energizing coil bobbin, emerging at opening 55 of the opposed side piece 54. Conversely, section 80 of magnetic member 78 enters the forward region of opening 55, extending through the forward region of longitudinal bobbin opening 63 and emerging at opposed side member opening 57.

It should thus be recognized at this point that the assembly of the electromagnetic structure is done in an extremely simplified manner as follows:

The L-shaped members 68, 78, housing side walls 56, 54, and bobbin 52 are all independently formed to provide the plurality of individual elements as shown in FIG. 4. The longitudinal opening 63 of bobbin member 52 is then placed in alignment with openings 55, 57 of the side members. The individual L-shaped magnet members 78, 68 are then placed therethrough to form a U about bobbin 12. The entire unit, which does not require any type of screws, stakes, or similar fastening means is then dropped into a suitable recess of the housing 18, with the appropriate electrical connections being made to coil ends 62, 64. With the unit so located, appropriate adjustment of screw means 43 is then made to calibrate the desired gap separation between bifurcated armature end 39 and the pole faces 76, 86.

Although a particular configuration of magnet, coil bobbin and side pieces is shown, it should naturally be understood that various other configurations may be constr-ucted in accordance with the novel aspects of our invention.

Although there has been described a preferred embodiment of this novel invention, many variations and modifications will now be apparent to those skilled in the art. Therefore, this invention is to be limited, not by the specific disclosure herein, but only by the appending claims.

The embodiments of the invention in which an exclusive privilege or property is claimed are defined as follows:

1. An electromagnetic structure comprising first and second magnet members each of a generally L-shaped configuration, and including planar first and second sections joined by a right angle bend, said first section having a principal planar surface extending in a first direction, and said second section having a principal planar surface extending in a second direction, perpendicular to said first direction, said magnet members nested together with the principal planar surfaces of first sections of said magnet members in juxtaposed, adjacent planar relationship and the principal planar surfaces of said second sections perpendicularly extending therefrom in spaced parallel planar relationship, to define a generally U-shaped configuration, such that said first portions form the body of the U, and said second portions form the arms of the U, an energizing coil in the form of a bobbin, having a longitudinally extending central opening communicating between first and second opposed ends thereof, said magnet members entering opposed ends of said central opening, such that said energizing coil is positioned between said U-arms, with said U-body passing through said central opening, said first sections freely positioned within said central opening in floating arrangement, such that upon energization of said coil their principal planar surfaces are electromagnetically drawn together in intimate contact engagement, said intimate contact engagement absolutely minimizing the spacing between the principal planar surfaces of said magnetic member for minimizing the reluctance of the joint.

2. An electromagnetic structure as set forth in claim 1, wherein the free ends of said second sections defining spaced magnetic pole faces, lying within a common plane, parallel to the body of the U, cooperating armature means positioned for movement towards or away from the common plane of said pole faces corresponding to the energization and de-ener gization, respectively, of said energizing coil.

3. An electromagnetic structure as set forth in claim 1:

further including a pair of generally planar side support members, one of said side support members positioned between the first end of said bobbin and the principal planar surface of the second section of said first magnet member; the other of said side support members positioned between the second end of said bobbin and the principal planar surface of the sec- 6 0nd section of said second magnet member, said side support members including an opening in alignment with said bobbin central opening, said side support member opening dimensioned to loosely receive said magnet members and permit movement thereof to said condition of intimate contact engagement. 4. An electromagnetic structure as set forth in claim 3: said side support members including locating means for positioning said electromagnetic structure in a cooperating housing structure.

References Cited UNITED STATES PATENTS 3,081,386 3/1963 Koenig et al 335-38 X 3,147,349 9/1964 Welch et a1. 335-125 3,167,693 1/1965 Hayw0rd 335-281 X 3,249,822 5/1966 Summers 335-276 20 BERNARD A. GILHEANY, Primary Examiner.

R. N. ENVALL, IR., Assistant Examiner. 

1. AN ELECTROMAGNETIC STRUCTURE COMPRISING FIRST AND SECOND MAGNET MEMBERS EACH OF A GENERALLY L-SHAPED CONFIGURATION, AND INCLUDING PLANAR FIRST AND SECOND SECTIONS JOINED BY A RIGHT ANGLE BEND, SAID FIRST SECTION HAVING A PRINCIPAL PLANAR SURFACE EXTENDING IN A FIRST DIRECTION, AND SAID SECOND SECTION HAVING A PRINCIPAL PLANAR SURFACE EXTENDING IN A SECOND DIRECTION, PERPENDICULAR TO SAID FIRST DIRECTION, SAID MAGNET MEMBERS NESTED TOGETHER WITH THE PRINCIPAL PLANAR SURFACES OF FIRST SECTIONS OF SAID MAGNET MEMBERS IN JUXTAPOSED, ADJACENT PLANAR RELATIONSHIP AND THE PRINCIPAL PLANAR SURFACES OF SAID SECOND SECTIONS PERPENDICULARLY EXTENDING THEREFROM IN SPACED PARALLEL PLANAR RELATIONSHIP, TO DEFINE A GENERALLY U-SHAPED CONFIGURATION, SUCH THAT SAID FIRST PORTIONS FROM THE BODY OF THE U, AND SAID SECOND PORTIONS FORM THE ARMS OF THE BODY U, AN ENERGIZING COIL IN THR FORM OF A BOBBIN, HAVING A LONGITUDINALLY EXTENDING CENTRAL OPENING COMMUNICATING BETWEEN FIRST AND SECOND OPPOSED ENDS THEREOF, SAID MAGNET MEMBERS ENTERING OPPOSED ENDS OF SAID CENTRAL OPENING, SUCH THAT SAID ENERGIZING COIL IS POSITIONED BETWEEN SAID U-ARMS, WITH SAID U-BODY PASSING THROUGH SAID CENTRAL OPENING, SAID FIRST SECTIONS FREELY POSITIONED WITHIN SAID CENTRAL OPENING IN FLOATING ARRANGEMENT, SUCH THAT UPON ENERGIZATION OF SAID COIL THEIR PRINCIPAL PLANAR SURFACES ARE ELECTROMAGNETICALLY DRAWN TOGETHER IN INTIMATE CONTACT ENGAGEMENT, SAID INTIMATE CONTACT ENGAGEMENT ABSOLUTELY MINIMIZING THE SPACING BETWEEN THE PRINCIPAL PLANAR SURFACES OF SAID MAGNETIC MEMBER FOR MINIMIZING THE RELUCTANCE OF THE JOINT. 